CY28405
Serial Data Interface
Data Protocol
To enhance the flexibility and function of the clock synthesizer,
a two-signal serial interface is provided. Through the Serial
Data Interface, various device functions, such as individual
clock output buffers, can be individually enabled or disabled.
The registers associated with the Serial Data Interface
initializes to their default setting upon power-up, and therefore
use of this interface is optional. The interface can also be
accessed during power-down operation.
The clock driver serial protocol accepts Byte Write, Byte Read,
Block Write and Block Read operation from any external I2C
controller. For Block Write/Read operation, the bytes must be
accessed in sequential order from lowest to highest byte (most
significant bit first) with the ability to stop after any complete
byte has been transferred. For Byte Write and Byte Read
operations, the system controller can access individual
indexed bytes. The offset of the indexed byte is encoded in the
command code, as described in Table 2.
The Block Write and Block Read protocol is outlined in Table 3
while Table 4 outlines the corresponding Byte Write and Byte
Read protocol. The slave receiver address is 11010010 (D2h).
Table 2. Command Code Definition
Bit
Description
7
0 = Block Read or Block Write operation
1 = Byte Read or Byte Write operation
(6:0)
Byte offset for Byte Read or Byte Write operation. For Block Read or Block Write operations, these bits
should be ‘0000000’
Table 3. Block Read and Block Write Protocol
Block Write Protocol
Block Read Protocol
Description
Bit
1
Description
Bit
1
Start
Start
2:8
9
Slave address – 7 bits
Write
2:8
9
Slave address – 7 bits
Write
10
Acknowledge from slave
10
Acknowledge from slave
Command Code – 8-bit ‘00000000’ stands for
block operation
Command Code – 8-bit ‘00000000’ stands for
block operation
11:18
11:18
19
20:27
28
Acknowledge from slave
Byte Count – 8 bits
19
20
Acknowledge from slave
Repeat start
Acknowledge from slave
Data byte 0 – 8 bits
21:27
28
Slave address – 7 bits
Read
29:36
37
Acknowledge from slave
Data byte 1 – 8 bits
29
Acknowledge from slave
Byte count from slave – 8 bits
Acknowledge
38:45
46
30:37
38
Acknowledge from slave
Data Byte N/Slave Acknowledge...
Data Byte N – 8 bits
Acknowledge from slave
Stop
....
39:46
47
Data byte from slave – 8 bits
Acknowledge
....
....
48:55
56
Data byte from slave – 8 bits
Acknowledge
....
....
Data bytes from slave/Acknowledge
Data byte N from slave – 8 bits
Not Acknowledge
....
....
....
Stop
Rev 1.0,November 20, 2006
Page 4 of 18
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